Ditch our firmware, run EMC2's RT code on our micros instead?

I've been reading about EMC2 lately, and running it in simulation mode as well. I'm becoming convinced that the smart thing to do is to throw all our firmware efforts away, and rewrite the RT portions of EMC2 to run on a microprocessor instead.

EMC2's understanding of acceleration and path following is MUCH, MUCH more sophisticated that what we have, or likely will have in the next 5 years unless we use their code. They even have implemented auto-calibration routines for stepper-based machines to find the maximum speed and acceleration on a per-axis basis.

I think it would wring considerably more performance out of our existing hardware, getting faster and more accurate prints than any other method. The only serious question I have is if it's even possible to reimplement it in that way, (does it require a floating-point hardware to get adequate performance?) and how beefy a micro it would need.

I know that we can use EMC2 right now with a parallel port, but adding more extruders or controlling the heaters requires dodgey workarounds, and heaven help you if you don't have a parallel port, or if your computer's hardware is a bit quirky, and can't do the low-latency stuff that EMC2 requires to function.

Current EMC2-type solutions to this require expensive dedicated IO cards, or older computers in the case of latency issues. EMC2 can't use the USB port approach because of latency issues. But the USB port with an external micro to run the RT code could get around this, and result in significant cost reductions for all users of EMC2, as well as nifty things like analog inputs, high-frequency PWM, and higher frequency stepping than is possible with current EMC2 implementations.

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I'm building it with Baling Wire

Counterproposal: just run linux.

http://www.robotshop.ca/bipom-arm9-gadgetpc-arm-linux-or-debian.html

http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=2556109&k=AT91SAM9260

The chip is $17.35 each, ~ $10 in large quantities, and that robotshop board is not too far in price from an arduino mega; presumably we could do up something like it with arduino mega pinouts ...

And then we'd have repraps that run linux, as providence intended.

I'm not proposing that particular chip, btw.

Edited 1 time(s). Last edit at 11/19/2010 03:41PM by SebastienBailard.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

I recently bought a second hand nokia e71, and was amazed at its capabilities, ( I am behind the times with mobile phones) It occoured to me that most people will have such devices, even in third world countries some day, if not already.

would it be possible to use them for reprap, we would still need drive boards but could a phone do the job of a computer?.

jgilmore, at the risk of upsetting people, I agree, I use mach3 for my cnc projects with an ancient laptop but will go over to emc2 when I can no longer download upgrades for free, but having said that its good that the boards have been developed,
at least to give alteratives.

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Random Precision

I have been looking into using a 32bit micro running Linux and EMC2. On closer inspection, the website lists the hardware requirements as X86 based processor. So at this point in time, they have not yet cross compiled it to run on other processors, let alone the completely different hardware I/O, PWM, and hardware timers that 32bit microcontrollers have to offer. It may some day be a good step up, but it looks like not for awhile.

Mike

Also part of the point of running EMC2 (besides the awesome path prediction and speed/acceleration stuff) is the cool GL visualizations of the toolpath, and pre-built machine interface (jog buttons, G-code command line, etc)
That couldn't (shouldn't) run on a stand-alone microprocessor.

Even with the X86 requirement, I'm sure there exists a stand-alone microcomputer based on a pentium or something. But to also run a openGL visualization interface w/ mouse and keyboard?

I think that's just silly. Not to mention moving away from the goals of low-cost and leveraging common hardware - the laptop with openGL that I (and many others) already have. Better to port the RT code to Cortex-M3 or something, and just pretend that it's still running under the host computers RTOS.

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I'm building it with Baling Wire